The full version of this paper is out, South Asian medical cohorts reveal strong founder effects and high rates of homozygosity. It’s not the best for understanding population structure because they focus on within South Asia variation, but it does seem to confirm that among Bengalis there is a cline from west to east, irrespective of religion (see the discussion where they note that Muslims in the west cluster with westerners). I found a PCA in the supplements where I added some explanatory notes. It’s really hard to parse their figures because they really didn’t care, and the Genomes Asia Consortium doesn’t release their data… (their browser sucks)
I would’ve flipped both axes on that PCA graph.